bombings and new arrests. Three men, college students, friends of the younger brother accused of terror. The three are in custody tonight and the charges, lying to federal agents, obstruction of justice and hiding items, including a backpack with empty fireworks. Abc's chief investigative correspondent, brian ross, has the latest on these three new people in this case. Reporter: The fbi has been suspicious of the friends since the day of the manhunt, when s.W.A.T. Teams raided the college campus and agents took two of them into custody on immigration charges. The two, both from kazakhstan, azamat tazhayakov taz and dias kadyrbayev had involved with dzhokhar tsarnaev to new york last year. Proudly posing in this snoop shot. The third had been a friend since high school. Tonight, the fbi says dzhokhar's friends recognized him immediately when those surveillance photos of the suspects were made public. We consider him to be armed and extremely dangerous. And. Reporter: And decided to help him. A lawyer denied the charges today. Immediately we dispute and we'll be looking forward to proving our case in court. Reporter: But the fbi says one of the teams and texted dzhokhar if he was the bomber. "Lol," dzhokhar responded. And then another exchange, "come to my room and take whatever you want." The fbi says the three went to dzhokhar's room that night at -- down this hall, to his third-floor room, number 7341. According to the complaint, they took a backpack containing fireworks with the powder removed, and dzhokhar's laptop computer. That night, there was that violent confrontation with authorities in watertown, and the manhunt for dzhokhar began. It was then, the fbi says, that one of the friends dumped the backpack and fireworn this dumpster behind their apartment in new bedford. The dumpster's contents ended up at a landfill where the fbi searched for three days and found what it saere these fireworks that the fbi says the -- now alleges the friends tried to hide. The fbi believes the powder from those fireworks was used to make the bombs. There's no indication the friends knew about the plot in advance. But in a footnote, one of the friends says dzhokhar told him a month before the bombing that he in fact knew how to make a bomb. Thank you, brian ross.

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